1. Field of the Invention
The present invention relates to the field of controlling a device. More particularly, the present invention relates to multi-modal control systems and methods for controlling the operation of a transport device.
2. Discussion of the Related Art
Human transport devices serve to move a person over a surface and may take many different forms. For example, a human transport device, as the term is used herein, may include, but is not limited to, wheelchairs, motorized carts, bicycles, motorcycles, cars, hovercrafts, and the like. Some types of human transport may include stabilization mechanisms to help ensure that the device does not fall over and injure the user of the transport device.
A typical four-wheeled wheelchair contacts the ground with all four wheels. If the center of gravity of the combination of the wheelchair and the user remains over the area between the wheels, the wheelchair should not tip over. If the center of gravity is located above and outside of the ground contacting members of the transport device, the transport device may become unstable and tip over.
Referring now to FIG. 1A, a typical wheelchair 100 is shown. The wheelchair 100 and the user 102 define a frame. The frame has a center of gravity 104 located at a position vertically disposed above the surface 106. The term xe2x80x9csurfacexe2x80x9d as it is used herein shall refer to any surface upon which a human transport device may sit. Examples of a surface include flat ground, an inclined plane such as a ramp, a gravel covered street, and may include a curb which vertically connects two substantially parallel surfaces vertically displaced from one another (e.g., a street curb).
The surface 106 may be at an incline as compared to the horizontal axis 108. The angle by which the surface 106 is offset from the horizontal axis 108 shall be referred to herein as the surface pitch and will be represented by an angle denoted as xcex8s.
The front wheel 112 and the rear wheel 110 of the wheelchair 100 are separated by a distance d. The distance d between the two wheels may be measured as a linear (e.g., straight line) distance. If the center of gravity 104 of the system is located at a position above and between the two wheels, 110 and 112, the wheelchair 100 should remain upright and relatively stable. The wheels 110 and 112 typically have opposing counterparts (not shown) on the other side of the wheelchair. The opposing counterparts may each share an axis with wheels 110 and 112, respectively. The area covered by the polygon which connects the points where these four wheels touch the ground (or the outside portions of the ground contacting parts, when the ground contacting part may cover more than a point) provides an area over which the center of gravity 104 may be located while the wheelchair remains stable. In various places in this discussion below this area may be referred to as the footprint of the device. The footprint of a device, as the term is used herein, is defined by the projection of the area between the wheels as projected onto the horizontal plane. If the center of gravity is above this location, the transport device should remain stable.
If the center of gravity 104 is vertically displaced above the surface 106 and outside the footprint (i.e., the projection of area between the wheels 110 and 112 onto the horizontal plane), the stability of the wheelchair 100 may decrease and the wheelchair 100 may tip over. This could happen, for example, when the wheelchair is on a surface that has a steep incline. When on a steep incline, the center of gravity 104 may shift back and cause the wheelchair 100 to flip over backwards. This is shown in FIG. 1B where the center of gravity 104 is located at a position that is outside the footprint of the wheelchair 100. The center of gravity 104 is shown including a gravity acceleration vector (g) which linearly translates the center of gravity 104 in a downward direction. The wheelchair 100 may rotate about an axis of the rear wheel 110 until the wheelchair 100 contacts the surface being traversed.
The user 102 may help to return the center of gravity 104 to a location that is above the area between the wheels 110 and 112 by leaning forward in the wheelchair 100. Given this limited control of the location of the center of gravity 104, it is clear that human transport devices such as wheelchairs may encounter great difficulties when traversing uneven surfaces such as a curb or steps.
Other types of human transport devices may include control mechanisms which allow the transport device to balance on two wheels. The two wheels may be connected to a single3 axis that passes through the center of the wheels. The axis connects the wheels in such a manner that the forward and backwards motion of the device is perpendicular to the axis. The control mechanisms may keep the device and the user in a stable upright position by driving the wheels forwards and backwards to keep the center of gravity located over the wheel axis. Such devices may additionally provide for locomotion by allowing the center of gravity to be displaced by a distance forward or backwards from wheel axis and having the wheels rotate in order keep the center of gravity located at that position. Examples of such devices are disclosed in U.S. Pat. Nos. 5,701,965 and 5,719,425 which are hereby incorporated by reference.
According to one embodiment of the present invention, a self balancing human transport device is disclosed. According to this embodiment, the transport device includes a movable arm and a ground contacting member coupled to the moveable arm. The transport device also includes a control unit to control movement of the arm in order to balance the transport device and to control movement of the ground contacting member in order to balance the transport device.
According to another embodiment of the present invention, a method of controlling a human transport device is disclosed. According to this embodiment, the method includes a step a) of moving an arm in order to balance the transport device. The method also includes a step b) of during step a) moving a ground contacting member in order to balance the transport device.
According to another embodiment of the present invention a human transport device capable of operating in a plurality of operational modes is disclosed. In this embodiment the transport device includes a rotatable cluster that has at least one ground contacting member and at least one actuator to move the cluster and the ground contacting member. In this embodiment the transport device also includes a control unit that provides a control signal to the actuator, the control unit providing the control signal such that the actuator causes both the cluster to rotate and the ground contacting member to move such that a center of gravity of the human transport device is located at a position vertically displaced between endpoints of the cluster.
According to another aspect of the present invention a transport device is disclosed. According to this embodiment, the transport device includes a control unit that provides control signals to the transport device such that a center of gravity of a system which includes the transport device and a user is displaced above a center of a footprint of the device, the footprint having a non-zero area.
In another embodiment of the present invention a method of controlling a transport device having a human occupant, the transport device having a cluster with wheels attached thereto and having a footprint whose area is greater than about zero is disclosed. In this embodiment the transport device is controlled by simultaneously controlling a position of the cluster and a position of the wheels such that a center of gravity of the transport device having a human occupant is located toward a center of the footprint of the transport device.
In another embodiment of the present invention a system for transporting a human across a surface is disclosed. In this embodiment, the transport device includes at least one moveable arm and at least one wheel attached to the at least one moveable arm. The transport device in this embodiment also includes a control unit that causes the movable arm to be moved in order to balance the system while rotating the wheels to propel the system.
In another embodiment of the present invention a method of controlling a transport device having a footprint with a non-zero area is disclosed. In this embodiment, the method includes steps of: a) moving a cluster of the transport device in order to balance the transport device, and b) during step a), moving a ground contacting wheel of the transport device to propel the device over a surface.
In another embodiment of the present invention, a human transport device operating in a plurality of modes is disclosed. In this embodiment, the transport device includes a control unit that changes a current operational mode of the transport device automatically, depending upon operational characteristics of the transport device.
In another embodiment of the present invention, a method of controlling a transport device such that the transport device remains in a substantially erect orientation while a platform of the device remains substantially horizontal regardless of a surface pitch is disclosed. The method of this embodiment includes a step of determining current operational characteristics of the transport device. The method of this embodiment also includes a step of automatically changing between a plurality of operation modes depending upon the current operation characteristics.
In another embodiment of the present invention, a control unit for controlling a device includes at least four wheels is disclosed. In this embodiment, the control unit includes a wheels controller that controls the rotation of the wheels. In this embodiment, the control unit varies the amount by which the wheels controller responds to user inputs based upon operational characteristics of the device.
In another embodiment of the present invention, a human transport device that returns to a stable state after a disturbance has been encountered such that a human user of the device remains in an upright position is disclosed. In this embodiment, the transport device includes user input that receives user-desired positional input commands, and a control unit that varies the responsiveness of the human transport device to the user input commands based upon a current orientation of at least one portion of the transport device.
In another embodiment of the present invention a method of controlling a ground transport device is disclosed. In this embodiment, the method includes steps of determining a value of an operational parameter of the transport device, and varying the responsiveness of the transport device to user inputs depending on the value of the operational parameter.
In another embodiment of the present invention a transport device is disclosed. In this embodiment, the human transport device includes a plurality of ground contacting members that may be moved in order to balance the transport device and a gain table containing at least two sets of gain coefficients. In this embodiment, the transport device also includes a control unit that applies one of the at least two sets of gain coefficients to inputs to the control unit in order to create a control signal which controls the movement of the wheels. In this embodiment, the set of gains applied by the control unit may vary automatically during the operation of the transport device.
According to another embodiment of the present invention a method of keeping a human transport device in an upright position as the transport device traverses uneven surfaces is disclosed. In the embodiment, the method includes steps of receiving user inputs, determining a current orientation of at least one portion of the transport device, and selectively applying different gain coefficients to the inputs based on the current orientation of the at least one portion of the transport device.
In another embodiment of the present invention a control system for controlling a human transport device is disclosed. In this embodiment, the control system includes a control unit that adjusts a cluster and at least one ground contacting member of the transport device such that a center of gravity of the transport device remains substantially vertically displaced over a location between end points of the cluster.
In another embodiment of the present invention, a method of switching between a plurality of modes in a human transport device is disclosed. In this embodiment, the method includes steps of determining a first value that represents a position of a center of gravity of the transport device, and selecting between two of the plurality of modes based upon the value.
In another embodiment of the present invention a method of creating a reference data set for use in estimating a location of a center of gravity of a device is disclosed. In this embodiment, the method includes steps of a) placing the device in a first position, b) recording a first position of a first component of the device while the device is in the first position, c) placing the device in a second position, and d) recording a second position of the first component of the device while the device is in the second position.
In another embodiment of the present invention, a method of determining a location of a center of gravity of a system is disclosed. In this embodiment, the method includes steps of placing the system in at least two positions where the system is balanced and recording an angular orientation of at least one component of the system at each position. In this embodiment, the method also includes creating a fitted curve which includes the angular orientation of the at least one component at each position.
In another embodiment of the present invention, a method of balancing a dynamic system is disclosed. In this embodiment, the method includes steps of receiving a data set which represents a desired orientation of at least one component of the system, and comparing the current orientation with the desired orientation. In this embodiment, the method also includes a step of adjusting at least one component of the system based upon a difference between the current orientation and the desired orientation.